Automatic means for maintaining a pump piston immersed in lubricating oil



Dec- 3, 1957 B. F. SCHMIDT AUTOMATIC MEANS FOR MAIMTAIMING A PUMP PIsToN IMMERSED IN LUBRICATING OIL 5 Sheets-Sheet l Filed Jan. 30, 1956 ATTORNEY Dec. 3, 1957 B. F. SCHMIDT 2,814,994

AUTOMATIC MEANS FOR MAINTAINING A PUMP PISTON IMMERSED IN LUBRICATING DIL 3 Sheets-Sheet 2 Filed Jan. 30, 1956 INVENTOR ATTORNEY Dec. 3, 1957 B. F. SCHMIDT 2,814,994

AUTOMATIC MEANS FOR MAINTAINING. A PUMP PIsToN IMMERSED 1N LUBRICATING OIL Ibn/EAITOR` enjamz'lrf S/nidi,"

ATTORNEY 5 Sheets-Sheet 3 Filed Jan. 30, 1956y thereof that are` contacted United States Patent @nice 2,8 l 4 ,9 94 "Patented Dec. L3, 1 95'] 258145994 `AUTOMATIC MEANS rFOR "MAINTAlbllNG1 A PUMP PISTON IMMERSED 'IN LUBRICAT- ING GIL Benjamin E. Schmidt,` LosAngeles, Cali-. Application January '30,` 1956,: Serial No.562,17'1

20 Claims. (Cl. 10S-179) This invention relates to pumps of the reciprocating piston type such as are employed in oil well operations, and has as Vits primary object the provision of a pump of this character in which the working surfaces of .thepiston are maintained'immersed in a body cil-lubricating oil; said oil` substantially retained in its -originalposition yand volumeby a body of mercury above andA below said oil, and protected against :mixing with abrasives due tothel presence of sand or Igritrontained in liquid beingpumped, `by the mercury operating as a seal or separator at all 4.points .between the liquid beingppumped and the sealingcoutactsiof the pump.

A particular object of the invention is toprovide a method and` an assemblage whereby fa body of .lubricating oi'lmay be conned in the working zoneiof apump .piston sogas to maintain as ubstantialbody of thelubricating oil between theweariug surfaces of the pump piston and contiguous walls of the pump whether externally of the piston or internally thereof.

Another object is` to provide a means whereby a` substantial volume of the lubricating oil will `be maintained in the pump at the opposite ends ofthe piston at :all times during operation thereof thereby insuring `functioning-of the` piston within 1a body of the lubricating oil throughout operation of the pump, and` also toprovide booster .means whereby such of the lubricatingoil asmay leak pastthe sealing rings and piston will be automatically `returned to the ,side of the pistonfrom whence it came.

Another object is` to provide fan arrangement whereby the body of lubricating oil will be confined :inirthepump between bodies of mercury in such manner as to prevent loss.. of` the lubricating, oil and thereby maintain, its` orign inalvolume, and` in` such manner that` `the mercury` will serve as a shield or barrier to prevent access tothe body of lubricating oil byliquid being pumped as well -asi solids contained in such liquid.

Afurther` object istoiprovide a pump embodyinga. piston body .the working face of which is` encompassed byia bodyfof lubricating oil entrapped in` the pumpby bodies ofmercury, wherein the pistonbody is,` sealed` at` all-.times in the` `lubricating oil, and its workingface maintained out of contact with themerc as distinguishedfrorn pumps embodying a mercury body in which `the piston` works.

An important feature of the` invention resides, niprovid.- inga` construction in the pump whereby thelseveralparts by:` mercury` are `coated withl av metal, such as silver or tin,` withwhich `mercury will coact to form` an` amalgam and thereby provide a` wiping contact between the mercury and the coated surfaces so as to prevent. fluids being` pumpedfrom adheringytothe surfaces of said pump parts yand thus prevent the; liquid' being pumped and solids contained, thereimfrom being drawn; into themercury and effecting contamination thereof.

With the foregoing objects iniviewy together with: such other: objects and advantages: asV may subsequently appeaxythe` invention resides in the parts and inf the com- 2` bination, construction land Iarrangement of parts Yhereinu after described` and claimed, and as illustrated by way yof example in the accompanying drawings in which:

Fig. lis a view in vertical section oa barrel type-@pis ton 'pump depicting the invention as applied withiportions broken away and showing the pump free ofiliqui'd;

Fig. 2 is a View in vertical section ofthe barrel portion of thepump shownin Fig. l, withiparts broken away;

Fig. 3 is alview in verticalsection partly inielevationof the pump piston shown in Fig. 1, parts beingibrokenaway;

Fig. 4 is a view in vertical section of a -booster-em ployed in conjunction with the piston shownin Fig. Sand showing it as detached;

Fig. 5 is a detail in'cross ysection taken on the lne^55 of Fig. l;

Fig. `6 is a detail in cross section as seen on `the line 6 6 of'Fig. 1;

Fig; 7 is a detail in cross section taken` ony the :line 7L-7 of'Fig. 4;

Figs. 8,9, and 10 are enlarged views 'in verticalsection respectively of the upper, intermediate and -lower portions of the pump shown in Fig. l, andillustrating 'the pump as equipped with a body of lubricatingoil-connedfin a body of mercury and'encompassing the pumppisto'n;

Fig. 11 is a modication of the construction shown in Fig. 8, the view being in verticalsection ywith parts :broken away of a piston pump in which the piston encompasses :a stand pipe and has an internalworking tace-presented fto the pipe, `and showing the manner of constructing the pump to carry out the invention;

Fig. 12 is an enlarged partial section; takenonfthefline 12-12 of Fig. 1l showing the structure equipped with' the body of lubricating oil and its confining Ibody of mercury;

Fig. 13 is a detail in 13-13 ofy Fig. 11';

Fig. 1,4 is a detail in 14 ,14 of Fig. 1l;

Fig. :15 is a detail in 15-15 of Fig. 1l; and

Fig. 16 is a detail in cross section talcemon. ftheline lr6-16 of Fig. l1.

Referring to the drawings more spediti-cally,- reference now being had to Figs. l to l0 inclusive,` Alindicalte's an upstanding cylindrical pump barreLB 4:designates Agenerall'/ the pump piston which is designed to be surroundediby and confined in part in a body of lubricating oil in 'said barrel, and C denotes a` booster which is associated with the `piston B for returning such oilfas leaks past th'e piston body back to the side from whence it` Came.

The, pump barrel A .as particularly shown inFifg. 2` is tted at its lower end in the usual man-ner with a conven tional intake section a and has its upper endleading toa point of discharge. The section Aa isformed witlr'aninlet a' from which leads a stand pip'e 18l eXtendi-n'g axial-ly of and spaced from the barrel AL equipped with a rfoot valve b` in an enclosing housing 17 andttedat its-upper end with Ia ball check valve 19 inI lacage 20, a-s is coinmon in oil-well pump construction.

In carrying out the invention as applied towthe bar-rel type'of pump, the barrel A istted on its interior" at a suitable point in the: length thereof with-a riedsl'eve 21` whichA encompasses the stand pipe 18fin spaced concentric relation thereto and is also spaced from the inner pe# riphery of the barrel A, the sleeve 21 beingiitted atfits upper end with a collar 22 which extends outwardrto the barrel A` and is attached to the latter a's` by screws 23 ywhich pass through openings 23' in the pump barrel and are threaded into engagement with the collar; At least one of the openings 23' is utilized as a means forintroducing lubricating oil into the pump, as willb'e later del `cross section `takenron theline cross section Ataken `on the `line cross section` taken on the" line scribed. Sealing rings 24 are disposed in the joint between the collar and barrel to render it leak proof. The collar 22 thus closes the upper end of the space 25 extending between the sleeve 21 and the barrel A.

The piston B is constructed as particularly shown in Fig. 3 and embodies a length of tubing 26 which is open at its ends and is arranged over the stand pipe 18 in spaced concentric relation thereto and has its upper portion leading longitudinally through the sleeve 21 in spaced relation thereto.

The upper end of the tubing 26 is screwed into a coupling 27 fitted with an end wall 28 engaged with the lower end of a pump rod 29 and embodying a cage 30 housing a ball check valve 31 normally closing an outlet port 32 in a septum 33 formed in the coupling 27.

The tubing 26 is formed intermediate its ends exteriorly thereof with a piston body 34 tted with a series of spaced sealing rings 35 bearing on the inner surface of the pump barrel A in the usual manner. The end portions of the tubing 26 constitute reduced diameter piston portions extending above and below the piston body. Rigidly mounted on the tubing 26 above the piston body 34 is a sleeve 36 which is open at its upper end and when assembled overlies the sleeve 21 in spaced telescopic relation thereto, the lower end of the sleeve 36 being closed by a wall 37 spaced a short distance above the upper end of the piston body 34. A series of passages 38 lead longitudinally through the piston body 34 which are normally closed at their upper ends by an annular plate valve 39 which seats on the upper end of the piston body 34 under the urge of an accordion spring 40 bearing between the valve 39 and the wall 37.

The passages 38 open to the lower end of the piston body to a space 41 lying between the barrel A and the lower portion of the tubing 26 as shown in Fig. 9, and which space 41 leads downward to the upper end of the booster C which latter is frictionally supported between the tubing 26 and the barrel A for longitudinal sliding movement relative thereto.

The booster C comprises a cylindrical shell 42 the upper portion of which encompasses the lower end portion of the piston tubing 26 and the lower end portion 26, whereby opening of the valve 48 is effected by the end of the tubing 26 being brought into engagement with the pins 53 and caused to depress the latter in opposition to the spring 52. The lower end of the tubing 26 is formed with open ended slots 54 through which the pins 50 freely extend with their inner ends projecting interiorly of the tubing 26 where they are engaged by the spring 52. The booster shell 42 is formed on the interior thereof with a longitudinal channel 55 slidably engaged by a projecting element 56 on the tubing 26 as shown in Figs. 6 and 10. A plurality of such channels and elements may be provided as occasion may require. The element 56 is here shown as comprising a threaded lug which is screwed into the tubing 26 and is formed with a recess in which is seated a spring 57 arranged to bear against the bottom of the channel 55 in frictional engagement therewith and thereby cooperate with the resilient rings 45 in yieldably and adjustably opposing relative movement of the piston tubing 26' and the booster shell 42. As a means for enabling assemblage of the element 56 in the channel 55, the shell 42 is formed adjacent the lower end thereof with apertures 58 arranged opposite the channel 55 through which the elements 56 may be passed and screwed into engagement with the tubing 26. The upper end of the channel 55 forms an abutment which serves in cooperation with the element 56to limit downward movement of the booster relation to the piston tube 26.

The above recited pump structure is designed to have the piston body 34 and the contiguous surface of the barrel A in the zone of travel of the piston body continuously submerged in and between bodies D-D of lubricating oil, the body D extending above the piston of which terminates in a narrow inturned ange 43 which f underlies the lower end of the tubing 26 and encompasses the stand-pipe 18 in spaced relation thereto.

The upper end of the booster shell 42 terminates in a piston head 44 having frictional engagement with the tubing 26 and the barrel A through the medium of resilient sealing rings 45 on the inner periphery of the piston head 44 and a resilient sealing ring 46 on the outer periphery of the piston head 44, The inner rings 45 are designed to have greater frictional engagement with the tubing 26 than the outer ring 44 with the barrel A thus creating a differential in the frictional engagement between the piston head and the tubing and barrel such that the piston head will tend to move with the tubing 26 yet be sealed relative to the barrel.

The space between the margin of the ange 43 and the stand pipe 18 constitutes a valve controlled passage 47 which is normally partially closed by a ring valve 48 formed on a sleeve 49 slidably encompassing the lower end portion of the shell 42, the sleeve 49 being tted with pins 50 which project through longitudinal slots 51 in the shell 42 and are engaged by a thrust spring 52 bearing on the flange 43 of the shell so as to seat the ring valve 48 over the passage 47 and partly close the latter. The Valve 48 is formed at the juncture with the sleeve 49 with a series of slots 48 constituting valve outlets oifset relative to the passage 47 and opens to the latter when the valve 48 is in its open position.

The ring valve 4S is fitted with a plurality of upstandingy pins 53 which extend through holes 53 in the flange 43, the upper ends of the pins 53 normally extending a short distance above the ange 43 in alignment with and in the path of travel of the lower end of the pistonv tubing body and completely lling the space surrounding the upstanding sleeve 36 on the piston body and partly filling the space surrounding the upper portion of the depending inner sleeve 21 and extending downward into the interior of the sleeve 36 a portion of the length thereof. The oil body D lies below the piston body and extends downwardly below the lower end of the latter to the upper end of the booster C, and also iills the passages 38 in the piston body. The oil bodies D-D meet in overlying relation to the piston body and completely encompass the working face of the latter by reason of leakage past the sealing rings 35 of the piston.

A third body D of lubricating oil occupies the upper major portion of the space exteriorly of the booster C, and below the piston head 44, and provides a sealing lm of lubricating oil on the inner face of the pump barrel; this oil body D" meeting a body of mercury occupying the lower portion of such space as will presently be described.

An important feature of the invention resides in collectively conining the oil bodies D-D-D between bodies of mercury E-F as shown in Figs. 8, 9 and l0, the mercury body E occupying the inner lower portion of the pump barrel A and extending upwardly from the lower end of the latter to a point submerging the lower portion of the booster C both interiorly and exteriorly thereof and submerging the lower end of the piston tubing 26 and meeting the lower end of the oil body D and the mercury body F being disposed in the pump barrel A above the xed depending sleeve 21 carried by the latter which body fills the sleeve 21 and the lower part of the sleeve 36, with a portion of the mercury body F extending into the space between the sleeves 21 and 36 and meeting the oil body D therein, this portion of the mercury body and the telescoped sleeves 21-36 forming a trap.

A column G of the mercury body E constituting an extension of the latter extends upwardly around the stand pipe 18 within the piston tubing 26 and terminates at a point below the valve 19 on the upper end of the stand pipe, the upper end of the column G and the sur' face of the mercury body F extending on substantially aser-,9er

adacentrplanes: whichdieuwell below the piston vals/e131 when, the` pistonris `in :its lowermost position; 'llhet relative levels ohmercurye column. Grand? thermercury body F vary# as the; pistommoves;` on its upstroke, the mercury body F moving up with thepistong,whilethecolumnG moves down.

The surfaces Kofy they pump partsfcontacted bythe mercuryfincluding4 ally tubes and extensionsfare coat-ed with,` a material, such as silveror theflike, with .whichwthef'mercuny,.will amalgamatef to' providez an` amalgam `coating to prevent fluids being pumped from adheringto theplated surfaces and also to, affordwaacleansing-actions during the pumpingoperation. The. several'. coatedsurfaces: are shown in sectionzby heavy lineswimFigs.4 2?;9` and 10; and are. indicatedV by` the reference charactervv yt, InY some` instances the coated surfacejfmay-` be formed by applying the:amalgamatingmaterial` directlyV to: thesurface byy a plating operation, while in some cases the pumprsurface involved may be-icovered by a thin llexibleisheet'ofmetal; such as copper.having a; plated", outer. surface.

In assemblying the. pump,` a: suitable quantity 'offmercury is. first poured into the pump; barrel' A to. partly formr the body E aroundthebaseofi the stand pipe:18,.whereupon afmeasuredrquantity,Y ofrlubricatingaoil is, pouredi into the pump barrel and imposed onithepreviously applied mer# cury to. later form `the oilbody D.`

The pump piston B free ofthe coupling 27-`and with thebooster assembled t. in: its lowermost position on the lower.A end thereof, is insertedvin thexupp'er end of` the pump.. barrel `and lowered zthereiniwuntil the lower end of the piston body 34fisr4 spaced. slightly above the upper end of the pump barrel. A measured quantity oflubri, caring; oil-Ais1 then poured into theA pump barrel beneath the piston body 3.4 `tot form the oilbodyy D? betweentthe lower end of the piston bodyl and theA upperend ofthe booster C. The piston; is again lowered to a point where theupperend kof thesleever is adjacent the upper end of the. barrel whereupon a` measured quantity ofmercury is poured into` the sleeve 36.1tofform the lower=portion of the mercury body F. The sleeve'21-A is then positioned around the tube 26 and heldsuspended with the latter with the ring 22 positioned slightly above the opening23. Aquantity of lubricating oil is then introduced through the opening 23 to lill the space 25 beneath the ring 22 abovethe piston body and above the previously applied mercury, within thev sleeve 36. The ring22 is` then Xed in place onthe pump barrel bymeans of the screws 23" whereby seating the openings 23.

The mercury body F is then built up to the desired level above the ring 22 and is preferably capped' by a floating expansible sand buffer ring 60. formedof rubber or the like and slightly spacedfrom the inner periphery of the barrel A and from the outer` periphery of the piston tubing 26, and forms'a bridge for supporting thereabove such sand and grit asmaybe de.- posited thereon settling from static liquid' in the pump barrel to prevent or at least minimize fouling orfcontamination of the mercury body F by such substances; the ring60 .being designed to expand laterally under pressure ofthe head of liquid being pumpedso as to have wiping contact with the pump barrel A and the upper extension 26 of the pump piston so that sand and grit may settle thereon as when the pump is idle, and thus be prevented from working down into the mercury andthe piston sealing'oil.

The piston is then shoved down to its lowermost position together with the booster C, which displacesthe pref viously applied oil then encompassing the booster' which moves upwardly into the space between the booster wall 42 andthe pump barrel to form the oil body D".` Air entrapped'between-the oil body D and the pistonhead 44'1is `exhausted through a vent A' formed in the pump. barrel atlaepoint just beneath the `piston head 44 when imitsdowermost-postion, andwhichvent'is then sealedA by arplugaAZz. @quantity ofmercuryf is;l thempouredznto the upper.: endnof the pistonk tubing. 26` from1which the coupling` 27`` isrdetached,` to:` substantially ll .the latter; mercuryY thusrapplied: forming'. the column G` in. continualtion' ofthe mercury body Thecoupling; 27. is.v4 then appliedtoxthe upper. endl of the tubingqZ after' whichwa section of4 pump? ro'd 29`7 s attached thereto and? sections thereo.I and `ofA the pump barrelfiA-w are assembledztorcomplete the pump. structure which isJoWered intoa-.well casing all in the usual manner;

AsV a means; fon` collecting` inewmetallicparticles.. such as are `abradedtfrom the: inner surface'of'the: pump;V barrel.l and `fori preventingl; such-A particles: from. being. circulated in the oil body,` Dv'andrthereby be:v causedto abradevthe working faces. `of the pump barrel-A= and piston'body` 34 the latter is equipped with magnetic traps1 comprisngrcir` cumierential.` channels-A 61M formed ats suitable: points in the pistonbody, .in which.channels.areimountedpermanent magnets-62^ adapted to attract metallic particles brought opposite the. channelsand cause them' to .be collected and retained in the channels for subsequentremoval...

As. afurthen means-.for collecting` such particlesait'rap therefon.isfprovidedrorr therupper end of the booster 'asV showrrin Fig, 1-0` which-` comprises an` annular basin: tftorrnedfofrresilient4 material having `a permanent magnet 64 arranged in. the bottomthereof 4for attracting and collecting'metallic. particles` settlingf over. `the: booster. C.

Inthe'operationrof-thepump shownrinFigs. lto lfOiinL- clusiveupward movement offzthe: piston B withiconsequent lowering of. mercury column G` effectsl intake: of' the liquid.- from the stand pipe (previouslyl tiled) past' the check valve 19-and1into.1the. piston tubingf26'.. Onrdown.-` stroke of the pistonfB-(check valve-19'then'ubeing'closem? entraps. thefliquidy inthe tubing 26` abover the mercury column 4G=so that asthe piston moves downwardly and mercury column G'moves up such. entrapped liquid' will' thenoW-past. the valve 31and-out of the cage: 30 into' the pump barrel' above the mercury body F. .During this downstroke: operation: the `mercury `column G .riseswithin the, tubing. 26 `toits uppermost position whenfthe stroke is completed, Continued reciprocation of the pump piston? eiects delivery ofthe: liquidthrough theA pump. barrel and' its ultimate discharge therefrom on the` up'stroke'iofrthe pump pistonin the manner common iny reciprocal pump.' operations.

On .upward movement of the piston the .columns of. lubricating; oil. D thereabove will inmost part belcausedI to move therewith causing displacement of the'roilimtlre upper portion of the space 25" sothatfav portionithereofi will move. downwardly into the space within thewupper.` portion of the sleeve 36 thus displacing` the` body of` mercury interposed between th'e sleeves 21ar1d".36;y and thereby. elevating` the mercury column F and `thercolumn of4 liquidv being pumped imposed thereon slightly' more` than the distance of travel of the piston.

During the upstroke of the piston B-the` lubricating oil. encompassing the piston body 34`andpossibly aportionroff the oil body D entrappedabove thepiston'body will leak. past.. the pistoni seals 35 and be addedto` the: body of. oil. D at thelower end of the piston body due to the high pressure of` the. head of' the liquid. beingA pumped5 thus increasingA the volume of oil between. the piston body 34 and thef upper end of the: boosterC, and thereby moving the latter downward suchdistance asv to accommodate the added oil, the booster movingdown-` ward while the piston moves upward against` thef resistance. of the resilientrings45 and springsy 57. However, on upward movement of the pump. pistonbody 34 -the body. of liquid therebeneath will move. bodily upward there-l with; the upwardly moving oil D being` followed by themercury body Esupplemented by mercury fromthefcolumn G which moves downward. and will. then pass to the lower end of the tubiugzandthrough the lowerfend of the booster C, the valve 49 opening under the urge or l n l 1 7 the down flow of mercury from the interior the tube 26 and of the booster shell 42, into 'the lower end of the pump barrel. However the parts at the lower end of the booster are of such loose lit on extension 26 as to permit the escape of a portion of the mercury from the lower end of the booster without opening the valve 49.

Downward movement of the booster C relative to the pump piston occurs during the upstroke of the piston B only under the influence of leakage of oil past the piston body of the booster C being designed to accommodate requisite longitudinal movement thereof under a maximum amount of leakage of oil past the piston body as will be likely to occur. Downward movement of the booster C may be limited by the upper ends of the channels 55 on the booster shell 42 abutting the projections 56 on the piston tubing 26.

At the peak of the piston upstroke and as the piston starts down pressures on the inner and outer columns of mercury are equal, and at this time the valve 48 on the booster C, if opened on the piston upstroke, will close under the urge of the spring 52.

As the pump piston B moves downward pressure is built up on the mercury body E beneath the piston body 34 by reason of valve 48 being closed and leakage past the valve 4S and standpipe being insufficient to take care of the mercury displaced by downward movement of the piston. Such pressure will act to force the booster C upwardly relative to the then downwardly moving piston, thereby forcing a portion of the oil body D beneath the piston body upwardly through the passages 38 past the valve 39 which latter opens under pressure of the oil therebeneath, thus adding such oil to the body D above the piston body 34 from whence it came.

The booster C is designed to function to effect delivery of a quantity of the oil from beneath the piston body to above the piston body equal that previously leaked past the sealing rings on the upstroke of the piston. Since the amount of such leakage is variable the action of the booster C must vary accordingly for which purpose its range of longitudinal movement is variable relative to the length of stroke and movement of the pump piston. This variable movement of the booster C is rendered possible by its frictional engagement with the piston for longitudinal movement relative thereto afforded by the rings 45.

- Upward movement of the booster C, relative to the downwardly moving piston B, due to pressure of trapped mercury body E, is limited by the lower end of the piston tubing 26 engaging the ilange 43 with consequent opening of the valve 4S and relieving the mercury pressure on the booster C.

This opening of the valve 48 places the mercury body E and mercury column G in free communication with each other so as to permit continued downward movement of the pump piston without further upward movement of booster C relative to tubing 26. The booster C will thus be disposed in its uppermost position on the piston tubing 26 when the piston B is in its lowermost position but on initial upward movement of the piston when the load of the liquid being pumped is directed through the mercury body F to the oil body D above the piston body through the trap afforded by the sleeves 21-36, then a portion of the oil body D may start leaking past the piston to force the booster downward proportionally to oil leakage, thus commencing another cycle of operation of the booster as above described.

Itis to be noted that the annular basin 63 on the upper end of the booster C will act in co-operation with the rings 45--46 to prevent or at least minimize the leakage of oil past the piston head 44 of the booster, which leakage however is further rendered negligible by reason of the ease of movability of the booster under the pressures of the leakage oil imposed thereon.

In the modied form of the invention depicted in Figs. ll to 16 inclusive, the same general combination of elements is employed as in the form shown in Figs. 1 to 10 inclusive except that in the modification an internal piston is employed which works on the standpipe instead of on the pump barrel.

In Figures 1l to 16 inclusive, H indicates the pump barrel, and I indicates generally the body of the pump piston which in this instance encircles the stand pipe I and has an inner working face cooperating with the outer face of the latter.

The pump barrel H is tted at its lower end with an intake section c screwed thereon and has its upper end leading to a point of discharge. The section cis equipped with a foot valve d in an enclosing housing e from which leads the stand pipe J extending axially of and spaced from the barrel H and tted at its upper end with a ball check valve f in a cage g. The upper end of the housing e is formed with a taper e. Mounted on the stand pipe I is a xed sleeve h which encompasses the stand pipe I in spaced relation thereto and is spaced inwardly from the pump barrel H. The sleeve h is open at its lower end and is closed at its upper end by a wall i.

The piston body I is formed on its upper outer margin with an upwardly extending cylindrical portion K which extends above the upper end of the stand pipe I and connects with a cage L attached to the lower end of the pump rod M. The cage L houses a foot valve N normally closing a passage O in a cap P on the upper end of the cylinder K which passage opens to the interior of the latter, the cap P constitutes the upper end of the pump piston.

Mounted on the piston I interiorly of the cylinder K is an upstanding sleeve j which extends upwardly interiorly of the downwardly extending sleeve Kh in spaced relation thereto; the sleeve j encircling the stand pipe I and spaced therefrom. The lower end of the piston body I is formed with a reduced tubular extension k which encircles the stand pipe I in spaced relation thereto. y

Mounted on the inner face of the piston body I is a series of piston seals l-l suitably spaced apart which seals slidably abut the stand pipe I. Formed in the piston body I is a series of elongated vertically extending chambers m which open to the upper end of the piston body through passages n and are closed at their lower ends by an annulus p detachably secured to the lower end of the piston I by bolts q. Leading from the lower end of each of the chambers m is a passage r formed in the annulus p which passage leads to the lower end of a passage s extending upwardly in the piston body I and opening to the interior of the latter adjacent to the upper end thereof through a port t located between adjacent pistons seals l-l.

The lower end of the passage s connects with a passage u leading to the lower end of the piston interiorly of the tube k which passage u is tted with a downwardly opening check valve v.

Mounted in each of the chambers m is a plunger w between which and the upper end of the chamber 1n is interposed an enxpansion spring x tensioned to yieldably oppose upward movement of the plunger w and to effect downward movement of the latter.

The lower portions of the chambers m beneath the plungers w are led with a body R of lubricating oil, as are the passages r, s and n. A column S of the lubricating oil lls the upstanding tube j and the upper portion of the depending tube h which column leads downwardly along the interior of the piston body l and connects (by leadage past the sealing rings .1 -F) with a column T of the lubricating oil leading downwardly a portion of the length of the tube k. The lower end of the oil column T in the tube k meets a mercury body U which extends into thev interior of the lower end portion of the tube k and occupies jointly with the oil body the space within the..

pump barrelHbeneaththe piston bodyl andalsoextends upwardlyin acolumn` Uf aroundy the-.piston body Land, around the` cylindrical `extension K` thereof to a pointv nearv but.` below the upper endlv thereof when the piston is in its lowermost position.J

Theinterior of the cylindrical extension Kris filled with a` bodyvof1 mercury V which extends upwardly into the sleeve h-tand meets the lubricatingoil therein; and which body of mercury V occupies the space interiorly of the cylinder. K, to a point below but adjacent to the valved upperend ofthe-stand .pipelt Thebody of mercury above the piston.body. I\ extendsf through the`passage. n. into the. spacerinthe' upper portion of the chamber.. m above the plunger w.

The' surfaces of the` pump structure. contacted by the mercuryare plated with a material, such as silver or the like` as. indicated aty with whichmercury will. amalgamatetto provide an amalgum coatingto prevent uids bev ing; pumped fromfadheringpto. the. plated surfaces and to also aiforda cleansing action during the pumping` operation.

Inassembling the pump shown `in Fig..` l1, thepiston I4 with the caps P and p removedis assembledon.thestand pipe l apartfrom the pump barrel H.by insertingthe pipe. I downwardly through. thetpiston I, the sleeve h: and; the valveassembly f-g being previouslyy attached to fthe, pipev J. The resultant assemblage is then placed: in the, pump` barrel H with the end. intake sectionc removed. wherefl uponthe. barrel with' the piston therein is invertedand lubricating oilis pouredinto-thethen. open ends` of. the chambers m andr passages. s to. ll them whereuponthe cap p l is applied to the lowerY end` of the. piston. A measuredA quantityk of oil is then pouredintothe tube lc after which the. intake. section c withthe valve d vand housinge thereon is screwed onto. the standy pipe l uponwhich the piston I isthen. positioned sotthat the tapered` ende. of theliousinge. abuts and'. closes the endiof the tube. lc. to t confineA the oil'` body therein.-

The intake. section. C is then'. screwed. oir-the` adjacent end of thepump barrel whereupon,theassemblage isright.- ed and a quantity of. mercury pouredintothe barrel. to( form the body U thereof.A Ameasured quantity of. mer.- cury is then poured in `the cylinder. K to formapontion of the` body V thereof, untilfitstands. at adesiredlevel in-ithe trap formedby the sleeve ht-JL Aplugz. inzthe` wall. ir is then removed and the chamber. below said wall and above` the mercury body V in thetrrap isthen `iilled with lubricating. oilto form the body S.- after. which theplug Z5 is replaced. Mercury is` then added to thefcylinder. Kto the required depth. A slight lift onthe pistontassembly unseats the tube k from the foot valve housing. e` where,- upon the mercury body U will entrap the `oil .bodytT conlined inthe tube k. The cap P is then appliedJ to thepiston cylinder K and connected to the. pump rod, Mi for operation.

I`n the operation of the. pumpshown inrFigs.` ll toltl6, inclusive the pumping action Yol? thepistonisfoppositethat ofthe pump shown in Figs.y 1 to l0 inclusive, inthatthe lift anddischarge ofthe liquid. beingpumpedtis `effected on the downstroke of the piston wrather` than onF the upstroke thereof.. In` this instance,M upstroke` ofrthe: piston. body Linducts the liquid being `pumpedfromA the vals/ed upper endr of'the stand pipe I into theupper endportiorr ofthe piston cylinder'K about the `mercury body. V there,- in; On downstroke of the piston body I the mercurybody Ulis displacedinto the columny U.' thereby;` elevating the. latter together with the pumped liquidi imposed. thereon and thus advancingtheilatter upwardly. to` discharge..

During the up anddown strokes ofthe. pump pistonthei entrapped oilbody S` above*` the piston body I will surge backA andi forth'in the traptformed byY the telescopedrsleeve; j` andihv,.while ther-oil: body T beneath the pistonf` body willtbe. carried up and' downin the piston extension k. Int this,v instance the:- builtLinchambers m` andlplungers` wf withA their;` associated?` partsi constitute; boosting means` 10 whereby the: oilbodiesV S` and `T will be maintained at uni-` formivolumes or. at. least` substantially so.` Thistis` ac.,- complished in the` following manner:

Onupstrokeot the` piston wherein the valve N- s main.-y tained closed, at negativefpressureis Vinduced within the piston which is impartedtothe mercury body V and. oil column S thus establishing negative pressure above` the plungers lw inthefchambers M. Downward pressure oi the liquid being pumped imposed on thefmercury column. U and `mercury bodyU is transmitted tothe: oiLbody, thereby forcinga portion of the latter upwardly.A past the. group of sealing ,rings l` below the port z.` Due. to` thel` resistance of Lsealing rings l" above the port t and` totnegaa tive pressure above tlieplungers m the oilleakingpam,theI ring sl will be induc.ted to pass through the ports` t and passages s-u into thechambers` m below the plungersw..

On downstrok'e, of. the piston when the valve N opens` pressures are equal above. and below the piston, so that the plungers w intthe chambers m willthen be advanced under the. urge of `the springtk (previously tensionedby. upward movement of thepl'ungersunder pressure of leakfage past the sealingrings l)y thereby forcing oil fromthe chambers m,through the check valve v back into the oil, body.. T and thus restoring the equivalent of the oil previ'ously frcedf-past `the sealing rings.

Generally considered', it will be seen that in each `of the` above described' applications of the invention the workingtfaceof the pump piston is maintainedsubmerged in a body of lubricating Voil which extends above, below,A and around the working face of the piston and is confined between separated bodies ofmercury` protected and held in placewithin the pumpbarrel in chambers plated with a material capable of `amal'gamating with mercury and. in

such. fashion that the piston will work at all times. with its,

workinglf'ace `lubricated by the lubricating oil: and. maili-` tained' out oflcontact with the mercury,` and `that the 11e-- cited. arrangement of trapsand seals allabrasives and solids. contained'in the liquid` being pumped, as. well? as` the. mercury, will be prevented: from, contacting orenter.-f ing. between the contiguous working surfaceof the bar,- rel and piston.

I.claim.:

l. In.a.n oilwelllpump,` a pump barrel', a.pi.ston.opera. tively `contained inV said barrel comprisingvta. pistonA bodyf having a reduced'di'ameter portion extendingbelow said` bodyL anda reduced diameter. portion extending above. said, body, saidiextensions, being` spaced from` said.` barrel, bodies of lubricating oil`conlineclin..said` barrelsurroundingl said piston and a part 01` said` reduced `diameter portionsvand Huid means preventing the `escape of. thel lubricating oil from sai-d' barrel and also preventing; the; mixingwith saidloh of liquid beingpumped, andpmeans; carriedlby the lower of saidreduced diameter. portions, for boosting` lubricatingoil. from` beneath to; above: said,

piston body to compensate for` leakage.V downward., past,

the pistontbody.

21 In an oil well pump, `a pump `barrels a, piston opera,- tvely contained in said barrel` comprisinga tubular, pis.- ton.body having.` an externally reduced. diametertubular endv portion extendingbelow said .body and ,anexternally reduced diameter tubular end; portion extending above saidbody, said" extensions being/ spaced from said bar-` rel, bodies offlubricating,oilconned.in.said barrel sur.- roundingwsaid piston and. portions.. oft. said.. reduced tdi:` ameter extension. andiiuidmeans preventing the escape, ofl the 1lubricating `oilfrorrrsaid .barrel andpreventing the mixing with said oil of A liquid.. being` pumped, said fluid; means consisting of two bodies ofmercury` oneof which is entrapped interiorlyA of saidA piston. and.l partially. eX-` ternally ofthe lower end portion ofthe lower piston extensionand the otherof'which is entrapped on the outside of the upper extension; of said piston; the surface of'the pump contacted by the mercuryy consisting of a material"` withA which/mercury will amalgamate.

3; Infan oilwell-lpump,` a-purnpbarrel; aholl'owpistonw operatively contained in said barrel comprising a piston body having a reduced diameter portion extending below said body and a reduced diameter portion extending above said body, said extensions being spaced from said barrel, bodies of lubricating oil confined in said barrel surrounding said piston and portions of said reduced diameter extensions, and means preventing the escape of the lubricating oil from said barrel and preventing the mixiing with said oil with the liquid being pumped; said means consisting of two bodies of mercury one of which is entrapped interiorly of said piston and partially externally of the lower end portion of the lower piston extension, and the other of which is entrapped on the outside of the upper extension of said piston, there being a trap in said barrel above said piston body comprising a pair of telescoping outer and inner sleeves, the outer sleeve of which is closed and affixed at its lower end to the upper end of said piston body and extending upwardly therefrom while the interior sleeve is fixed at its upper end to the pump barrel and extends downwardly in laterally spaced relation to the outer sleeve on the piston body; the upper end of said inner sleeve being open interiorly to said pump barrel and being sealed exteriorly thereof to said pump barrel the lower portion of the space between said sleeves being lled with mercury and the upper portions of the space between said sleeves being illed with lubricating oil, the surf-aces of the pump contacted by the mercury consisting of a metal with which the mercury will amalgamate.

4. In a pump embodying a barrel, having a valved inlet at its lower end, a stand pipe in the barrel leading from the valved inlet and fitted at its upper end with a check valve, and a tubular piston in said barrel encompassing said stand pipe having a valved upper end above the stand pipe connected to a pump rod; said piston having a body portion fitted with external sealing rings slidably engaging said barrel and being submerged in a body of lubricating oil, and mercury bodies conning said lubricating oil and separating it from the liquid being pumped; the surfaces contacted by the mercury consisting of silver.

5. The structure called for in claim 4 in which lubrieating oil above the piston body is subject to leaking past the piston sealing rings under pressure of the head of liquid being pumped, together with booster means carried by said piston and controlled by movement thereof operable to return the equivalent of the leaked oil back to the oil above the piston.

6. In a pump embodying an upstanding barrel having an inlet at its lower end, a stand pipe in the barrel leading from the inlet, a foot valve in the lower end of said stand pipe normally closing the barrel inlet, a check valve at the upper end of said stand pipe, and a hollow piston in said barrel into which said stand pipe extends; said piston inclu-ding a body portion carrying sealing rings and having tubular extensions of reduced external diameter on its upper and lower ends, the extension on the lower end of the piston being open and the extension on the upper end of the piston extending above the upper end of the stand pipe being fitted with a traveling valve and connected to a pump rod; an inner sleeve in said barrel fixed at its upper end relative thereto above said piston body, said sleeve being externally closed at its upper end to said barrel and open at its lower end, a sleeve carried by said piston telescoped relative to said first named sleeve and spaced therefrom; said outer sleeve being closed at its lower end and opening at its upper end to said pump barrel, a body of mercury entrapped in the lower end portion of said pump barrel extending upwardly around the lower portion of the tubular extension on the lower end of said piston body and extending interiorly of said piston around a major portion of the length of said stand pipe, a second body of mercury above and carried by said piston body extending upwardly around the lower portion of Cil said upper piston extension and between said telescoped sleeves, and a body of lubricating oil interposed between said bodies of mercury extending into the lower of said tubular extensions and overlying the outside of the piston body and extending above said piston around said telescoping sleeves and meeting the mercury between said sleeves; the surfaces of the pump contacted by the mercury being forme-d of a material with which the mercury will amalgamate.

7. The structure called for in claim 6 together with means carried on and controlled by the lower extension of said piston body for boosting oil from beneath to above said piston body to compensate for leakage of said oil downward past the sealing rings.

8. In a pump embodying an upstanding pump barrel having an inlet at its lower end, a stand pipe in said barrel leading from said inlet, a foot valve in the lower end of said stand pipe and a check valve at the upper end thereof, and a hollow piston body in said barrel into which said stand pipe extends; said piston body including a cylindrical body portion having sealing rings on its outer periphery and having axial tubular extensions of reduced internal diameter on its upper and lower ends encompassing said stand pipe, the extension on the lower end of the piston being open and the extension on the upper end of the piston extending above the upper end of said stand pipe, said upper extension being fitted with a traveling valve, and connected to a pump rod and being open to the pump barrel above said traveling valve; said piston body being formed with longitudinal passages leading therethrough, a spring pressed valve carried by said piston normally closing said passages, a body of lubricating oil in said barrel overlying the upper end and side of said piston body, and a second body of lubricating oil underlying said piston body, a mercury body in said pump barrel underlying the oil body beneath the pistou body, a mercury column in said tubular extensions imposing pressure on said second body of oil, and a booster element in said barrel carried by said lower piston extension and spaced beneath said piston body operable by the pump head pressure on said mercury to force lubricating oil from beneath said piston body through said passages to the body of oil above said piston body; the surfaces of said pump contacted by the mercury being formed of a material with which mercury will amalgamate.

9. In a pump embodying an upstanding pump barrel itted at its lower end with an intake section formed with an inlet, a stand pipe leading from said inlet equipped with a foot valve at its lower end; a tubular piston in said barrel encircling said stand pipe having an enlarged cylindrical tubular piston body carrying sealing rings on its outer periphery and having tubular extensions on its upper and lower ends encompassing said stand pipe, and a valved connection between said upper extension of said piston and a pump rod; said piston body having a valved passage extending longitudinally therethrough, a mercury body in said barrel submerging the lower end portion of the extension on the lower end of `said piston, said column of mercury extending between said piston and said stand pipe to near but below the upper end of the latter; a body of lubricating oil in said barrel beneath said piston body encompassing a portion of said lower extension above a lower portion of said mercury body, a second body of lubricating oil entrapped above and surrounding said piston body, a second mercury body in said barrel sealing said entrapped second body of lubricating oil from liquid being pumped and acting under hydraulic pressure to irnpose `a load thereon tending to force oil from said second body past said piston to the underside thereof, and a booster means in said barrel carried by said lower extension beneath said piston body for boosting lubricating oil from beneath said piston body through the passage in said piston body into the oil body above said piston, said means embodying a tubular shell encompassing the lower extension of said piston having a piston head submerged attesa in the .foil body beneath-.thegpiston `body and having a valved .lower-end submerged in-thelmercury body beneath saidioilbody,gsaidfpiston head .having .outer sealing rings engaging said` pump .barrel and innerV sealing rings engaging` said lower extension,` said piston head andshellbeing moveable relative, .to said. piston `body under urge of pressure imposed .on the mercurybody Vtherebeneath to elevate saidpiston head, and. means frictionally :carried by said,lower.. extension wherebyrdownwardmovement `of said piston will move said piston head and shell `to discharge.leakedwoildownwardly; the surfaces of the pump contacted, by the mercury being formed.. of a metal with which the .mercury will amalgamate.

10. In a pump, apump barrel, a reciprocal piston thereinhavinga tubular pistonbody formed with a longitudinal passage therethrough an .upwardlyopening valve on said piston body normally closing. said Jpassage, a reduced diameter tubular .extension .on the lower .end of. said .piston body, a body of .mercuryentrapped in .the lower end of said pump lbarrel,.,a.column ofmercury. in said piston and extension .meeting said body of mercury, a booster element in` said barrel.encompassing;aud..carried by said extension having a. piston .head sealed against said barrel and against said. extension, a body of4 lubricating .oil beneath saidpistonthead.extendingbetweensaidpiston head andsaidbodytof mercury, ,and a body `of .lubricating oil extendingabovethe upper end of said .piston body and surrounding the latter and subject to leaking, .past said piston body .into tthe oil body beneath said .piston body and then .displace said `booster element downwardly; Isaid booster element being moveableupwardly under fluid pressure imposed thereon by .said mercury column to force oil `from said last named-,oil Ibody through. said passage to above said `piston body; the .parts of the pump contacted by said bodies `ol? mercury and said column of mercury being surfaced with a aterial .with which mercury will amalgamate. l

\11,`. In apump,a barrel having upper and 4lower portions of its Ainterior surfaced with silver, .an upstanding silver coated stand pipe in said barrel` having a` valved end,` a tubular VVpiston body telescopingsaid stand pipeand slid'ablyrcontacting. said barrel, reduced tubular extensions on `the upper andlowerends of said piston body having their inner and outer surfaces silver coated, a coupling on the upper end of thenpper extension for connection with a pump rod, a valve` in said coupling normally closing said upper extension, a body of lubricating oil in said barrel4 overlying each .end .of said piston body and surrounding .the `inner end portions of said extensions, mercury bodies. confining said bodies of oil and preventing contamination thereof by fluid being pumped, and means carried by said. .lower extension for creating an upward pressure on the body of oil beneath the piston body on downward stroke of the latter to force a portion thereof past the piston into the oil body above the piston body.

12. In a pump, a barrel having its lower and its upper interior surfaces plated with silver, an upstanding silver plated valved intake tube in said barrel, a silver plated tubular piston having a body in slidable sealing operative contact with said barrel telescoping said intake tube in spaced relation thereto and having silver plated reduced end extensions above 4and below said body, a valve attached to and closing the end of said silver plated extension above said tube and providing a connection for a sucker rod, said reduced piston extensions spaced from said barrel to provide chambers above and below said piston body, a valve controlled passageway connecting said chambers for returning to the upper chamber 1eakage that may occur from the upper chamber to the lower chamber, a body of lubricating oil in each of said chambers, a booster piston in said lower chamber within the lower body of lubricating oil and mounted on the lower piston extension and arranged to position itself according to' the quantity of oil in said chamber and connected control valve controlled by the downward movement of. said booster, `a pair .of spaced .outerfand .inner telescop` ing .silver platedtubes'above.said piston the innerof which issealingly'conneoted to-said .barrel in the upper chamber and y`having .upper rand lower. ,ends andA the outer .of which israttached tosaidpiston and .havingfa closed lower end andnn topen upper end,` said Vtubes being. arranged to telescope, each .other .tovarying degrees according to :the position in said barrel of said piston, the oil in the upper chamber .extending ,.intothe. spaces .between said telescoping.tubes,..a ,body ofmercury in said :silver plated pump barrel abovesaid .piston body between the barrel and the reduced .upwardextension` ofthe `.piston and. encompassing the-telescoping tubings and4 meeting `the lubricating oil in said. tubing` interiorly ,of one `of. said tubes to effect a yieldable seal for the upper .oil chamber and serve as a protector against pumpedfiuidfrom entering said lubricating oil, abody offmercuryinteriorly of said silver plated piston extending downand .around the silver plated upstanding tube andfilling the space `below said piston body and entrappingthe lubricating oil above and below said booster piston, a valve controlled by the movement of mercury urgngsaid booster piston to move upwardly returning any oil leakage through said valve controlled passage when pumping action movessaid tubular piston downwardly, said mercury in cooperation with the silver lined piston ytubesand extensions affording a trap 'for the lubrieating-dil` and a seal preventing the pumped oil from intepm'ixing with the lubricating oil'.

1,31. In anoil wellgpumpV a partially silver plated pump barrel, an upstandingsilver plated intake tube fitted with a pair `of normally closed upwardly opening valves, a hollow sil-verplatedpiston in said pump barrel telescoping said` tube and spaced therefrom to provide a Huid workingchamber, said` pist on havinga reduced lower extension and also areduced` upper extension provided with a normally closed upwardly opening valve, each of said extensions being silver plated interiorly and exteriorly, said` extensions being` spacedfrom said pump vbarrel forming ,an -upper chamber and a lower chamber each of which i's provided with a quantity of lubricating sealing oil for lubricating the working contacting surfaces of the piston and `barrel, a silver platedouter sleeve sealingly attached to the piston and extending openl end up, a silver plated sleeve open at .its end and sealingly attached to the barrel, saidlast namedsleeve telescoping said first named sleeve in spacedrelation thereto, the oil in said upper oil chamber extending up into the telescoping silver plated sleeves, a body of mercury between the upper piston extension and thepump barrel trappingcsaid upper body of lubricating oil in the telescopingtsleeves permitting rise and fall of the oil in the `spaces provided yet preventing loss of said oilor intermixing with pumped Huid, a body of mercuryinteriorly `of said hollow piston and. extending downward and beneath the piston body to the wall of the silver plated barrel protecting said lower body of lubricating oil against loss by leakage and preventing pumped oil from contacting said lubricating oil, and a booster carried by said lower piston extension for returning quantities of lubricating oil from one chamber to another during a pump stroke operation, there being a valve controlled passage in said piston connecting said chambers.

14. In an oil well pump embodying a pump barrel, a reciprocating piston in said barrel having a reduced upper end portion, and a body of mercury in said barrel interposed between said piston and liquid being pumped and surrounding said end portion and an expandable butter ring oated on said mercury body.

15. In an oil well pump, a pump barrel, an upstanding valved intake tube in said barrel, a hollow piston telescoping said standing tube and spaced therefrom providing a fluid dow passageway, said hollow piston having a body in operative, contact with said barrel, a body of sealing lubricating oil in said pump barrel above said piston body, a body of sealing lubricating oil in `said pump barrel imw mediately below said piston body, a body of mercury conned in said pump barrel immediately below the lower oil body a body of mercury above said piston body, and trap means carried by said barrel and piston and arranged above said piston for preventing the mercury above the piston from contacting the barrel and preventing the lubricating oil above the piston from contacting the oil being pumped.

16. ln an oil well pump, a pump barrel, an upstanding valved intake tube in said barrel, a hollow piston telescoping -said standing tube and spaced therefrom providing a iluid ow passageway, said hollow piston having a body in operative, contact with said barrel, a body of sealing lubricating oil in said pump barrel above said piston body, a body of sealing lubricating oil in said pump barrel irnmediately below said piston body, a body of mercury confined in said pump barrel immediately below the lower oil body a body of mercury above said piston body, trap means carried by said barrel and piston and arranged above said piston for preventing the mercury above the piston from contacting the barrel and preventing the lubricating oil above the piston from contacting the oil being pumped, and a flexible buffer ring on the upper surface of upper body of mercury.

17. In an oil well pump, a pump barrel, an upstanding valved intake tube in said barrel, a hollow piston telescoping said standing tube and spaced therefrom providing a fluid ilow passage way, said hollow piston having a body in operative, contact with said barrel, a body of sealing lubricating oil in said pump barrel above said piston body, a body of sealing lubricating oil in said pump barrel immediately below said piston body, a body of mercury confined in said pump barrel immediately below the lower oil body a body of mercury above said piston body, and trap means carried by said barrel and piston and arranged above said piston for preventing the mercury above the piston from contacting the barrel and preventing the lubricating oil above the piston from contacting the oil being pumped, all pump lsurfaces contacted by mercury formed of a material with which mercury Will amalgamate.

18. in a pump embodying an upstanding pump barrel itted at its lower end with an intake section formed with an inlet, a stand pipe leading from said .inlet equipped with a foot valve at its lower end and a check valve at its upper end; a tubular piston in said barrel encircling said stand pipe having an enlarged cylindrical tubular piston body carrying sealing rings on its inner periphery contiguous said standpipe, a tubular extension on the lower end of said piston body encompassing said stand pipe and spaced therefrom; a body of mercury confined in said pump barrel submerging said piston body and said extension, a body of lubricating oil interiorly of said extension meeting said mercury body extending interiorly of iti said piston, a body of lubricating oil entrapped above said piston and meeting said rst named body of oil; said first named body of oil being subject to being forced upwardly past said piston body interiorly thereof under pressure imposed on said mercury body, and booster means carried by said lower end extension of said piston body for forcing return of said oil to its original position; the surfaces in said pump contacted by the mercury being covered with a material with which mercury will amalgamate.

19. The structure called for in claim 18 wherein said last named means comprises a chamber in said piston body, a passage leading from the lower end of said cha-mber to the inner upper portion of said piston, a plunger in said chamber, a body of lubricating oil in said chamber beneath said plunger and iilling said passage, and springs bearing between said piston and plunger for depressing said plunger to force oil from said chamber through said .passage to the interior of said piston.

20. ln an oil well pump embodying an upstanding pump barrel, a tubular piston operatively contained in said barrel, a lower end wall on said pump barrel having an inlet passage fitted with a foot valve, a stand pipe leading upwardly from said inlet through said piston to a point thereabove having its upper end fitted with a check valve, a pair of spaced tubular sleeves telescopically arranged in said barrel above said piston including an outer sleeve and an inner sleeve, said outer sleeve having an open upper end and being closed at its lower end and affixed to said piston, said inner sleeve being open at its ends and lhaving its upper end xedly connected to said pump barrel in sealed engagement therewith; a lubricating oil body surrounding said piston and extending immediately above and below said piston with the oil body above said piston surrounding and extending above said outer sleeve and filling the upper portion of the latter, a body of mercury in said outer sleeve beneath the oil therein filling said inner sleeve and extending into the space in said pump barrel immediately above the upper end of said sleeve and a second body of mercury trapped in the lower end portion of said pump barrel immediately below the body of lubricating oil and extending upwardly into said hollow piston around said stand pipe.

References Cited in the file of this patent UNTED STATES PATENTS 1,801,304 Carson Apr. 21, 1931 1,929,451 Schmidt Oct. 10, 1933 1,934,740 Schmidt Nov. 14, 1933 1,953,439 Schmidt Apr. 13, 1934 2,669,190 Mullens Feb. 16, 1954 

